As shown in FIG. 1, an eye 10 includes a cornea 11, an iris 12, ciliary muscles 13, ligament fibers or zonules 14, a capsular bag 15 that encloses a lens 16, and a retina 17. The lens 16 is composed of viscous, gelatinous transparent fibers, arranged in an “onion-like” layered structure, and is disposed in the transparent elastic capsular bag 15. The capsular bag 15 is joined by the zonules 14 around its circumference to the ciliary muscles 13, which are in turn attached to the inner surface of eye 10.
In an isolated state, the relaxed capsular bag 15 and lens 16 takes on a nearly spherical shape. When suspended within the eye 10 by the zonules 14, however, the capsular bag 15 moves between a moderately convex shape (when the ciliary muscles 13 are relaxed) to a highly convex shape (when the ciliary muscles 13 are contracted). For example, as shown in FIG. 2A, when the ciliary muscles 13 relax, the capsular bag 15 and lens 16 are pulled about the circumference, thereby flattening the lens 16 along a vertical axis. When the ciliary muscles 13 contract, the capsular bag 15 and lens 16 relax and become thicker along a horizontal axis, as shown in FIG. 2B. When the lens 16 assumes a more spherical shape, the diopter power of the lens 16 increases. Because the shape of the lens 16 can change, it is referred to as an accommodating lens in that the focal length can change to provide a sharp image at varying distances, near and far.
An intraocular lens (“IOL”) is a medical device that can be implanted into the eye 10 to replace the natural lens 16. The IOL can be implanted in an intact or partial capsular bag 15. The IOL is positioned and secured in the eye 10 by one or more haptics. The IOL and haptics can be made as separate pieces attached together, or as a single integrated piece. Typical IOLs are manufactured from polymers, such as polymethylmethacrylate, polypropylene, or foldable materials such as silicone, hydrogel or acrylic.
Conventional IOLs, however, are limited. Some provide sharp vision at only one distance, that is, they have a fixed focal length or are monofocal. Other IOLs provide two or more focal distances (“multifocal lenses”) and thus allow sharp vision at several distances but at the expense of contrast and sharpness as compared to a monofocal lens. For many multi-focal IOLs, only certain distances are in focus, with intermediate distances always being out of focus. Neither of these IOLs is an accommodating lens because the focal length(s) of the lens is fixed.
In some instances, accommodation can be simulated in IOLs. For example, the refractive power of an IOL can change by varying the IOL's shape, by moving the IOL along an optical axis, or by shifting several optical elements towards or away from one another. While these types of solutions can be and have been implemented in external corrective vision systems, such as spectacles or glasses, they are more challenging to implement within the eye, and particularly within the capsular bag 15.